How to set overall opacity for a particle system?

Development Rendering
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1

Hi There,

I have a particle system that fades particles in and out during their lifetime using the particle editor. I would like to scale the overall opacity of the system, so that I can fade it in and out as a whole.

Right now I’ve done this (I think, still WIP and untested) by adding a dynamic material instance with an extra opacity multiplier. However this approach seems overly heavy as it operates on a per pixel level and there is already an opacity blend in there that it would be nice to leverage.

Is there a way I can do this without the material instance and extra per pixel operation?

2

Looks like there’s an alpha scale parameter… A new, community-hosted Unreal Engine Wiki - Announcements - Epic Developer Community Forums

I’ll try that now.

The MID approach seems like it should work and is useful for more custom effects but while I can set the opacity value in the material instance editor and have it work from C++ it doesn’t seem to have any effect:

		MyParticleMID->SetScalarParameterValue(TEXT("Opacity"), 0.2f);
3

Following the instructions in A new, community-hosted Unreal Engine Wiki - Announcements - Epic Developer Community Forums allows me to set alpha via C++, am still interested in what I’m missing with the MID.

	MyParticleComponent->SetFloatParameter("AlphaScale", 0.5f);
4

If you select the Required node of a particle and make an instance of the material being used then add in a multiply from the alpha and connect the alpha to A and a Scalar Parameter to B and name the scalar Opacity, you can change the particle to use your material instance and then control the opacity however you like (real-time or not) through the material instance.